The acetylcholine receptor is a critical determinant of the function of the neuromuscular junction in both the normal and in diseased states. The goal of this research is to obtain basic information on how certain properties of the receptors, i.e., receptor affinity, specificity and channel formation are determined by the chemical structure of the receptor protein. The research approach is the use of chemical modification of specific structural groups on the receptor and the correlation of this with changes in the functional properties measured electrophysiologically. To date, electrophysiological procedures and computer programs for voltage clamping and noise analysis at the neuromuscular junction have been accomplished and control values for mean open channel time and conductance measured. Experiments to determine changes in these parameters after treatment with sulfhydryl reagents are in progress.